Clashes between supporters and opponents of Moammar Gadhafi were reported in Tripoli, Libya's capital, Sunday as the Libyan leader tried to squelch the uprising against his 40-year rule.

Witnesses in Libya's second-largest city, Benghazi, said Sunday that some military personnel there had switched sides and joined the anti-government demonstrators in the city, where security forces have reportedly shot and killed scores of protesters over the past week.

Earlier Sunday, a U.S.-based rights group Human Rights Watch said Libya's death toll from five days of unrest had risen to at least 173.

Sources at hospitals in Benghazi said the crackdown there has killed at least 200 people and wounded hundreds of others.

Raw protest video from Libya:

In the first-reported defection from Mr. Gadhafi's regime, Libya's representative to the Arab League quit to protest the harsh crackdown against the demonstrators. Libya currently holds the rotating presidency of the 22-nation group.

U.S. State Department spokesman P.J. Crowley says the U.S. is "gravely concerned" by "credible reports" of hundreds killed or injured in protest-related violence.

Meanwhile, the Arabic satellite channel Al Jazeera says the Libyan government has blocked Al Jazeera's television signal in the country. The channel's coverage has played a big role in protests across the region.

There was no independent confirmation of Libyan witnesses' accounts of the violence, as the government has barred local and foreign journalists from covering the unrest.

Libyan authorities also cut off Internet services in the country Saturday, denying cyber activists a key tool to mobilize demonstrators.

Mr. Gadhafi has tried to defuse the protests by doubling the salaries of state employees and releasing 110 suspected Islamic militants. He took power in a 1969 coup and has built his rule on a cult of personality and a network of family and tribal alliances.

Some information for this report was provided by AP, AFP and Reuters.

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